1. Field of the Invention
The invention relates to a keyboard for a control box of an electric apparatus.
2. Description of Pertinent Information
Traditional keyboards for control boxes of electrical apparatuses such as calculators and telephones generally comprise plastic bearing keys provided with metallic contact pads which act on a printed circuit.
The keys of these traditional keyboards are biased in their resting position out of contact with the printed circuit by springs.
As these keyboards evolved, the springs were eliminated by using a sheet of contactors made of non-conducting silicone, each contactor projecting from the sheet through a blister forming a spring. The metallic pads were then advantageously replaced with pads made of conducting silicone.
In these apparatuses, the plastic keys are guided by and rest upon the contactors.
Other types of keyboards were also developed in which the keys are directly molded with the sheet of contactors. In these keyboards the keys are also made of silicone.
Both types of keyboards suffer from disadvantages. One of the disadvantages of the apparatuses in which the keys are separate from the sheet of contactors, resides in the need and difficulty in assembling these separate elements in the box, whereas the keyboards are generally made and delivered separately.
The apparatuses in which the silicone keys are integrally formed with the sheet of contactors have, on the other hand, the disadvantage of reducing disposable space under the sheet.
If to remedy this situation, the interior of the keys are hollowed out to gain space, they then risk not being sufficiently rigid, particularly when the keys are provided with several contact pads.
Finally, it is impossible, with both types of keyboards, to light the keyboard with luminescent diodes without resorting to complicated or cumbersome apparatuses using double printed circuits, for example.